Note: Descriptions are shown in the official language in which they were submitted.
~$6~07
Exhaust muffler for a motor
vehicle or the like
Tne present invention relates to catalytic exhaust
mufflers which comprise,inside a metal case defining gas
inlet and outlet chambers, a body of a ceramic material,
of the honeycomb or like type, which treats the gases and
which must consequently be passed through by the whole of
the latter. Now, i~ is well known that the ceramic mate-
rial is extremely fragile and it is therefore necessary to
protect it against risks of deteriora-tion due to vibrations
under~one by the exhaust mu:Efler or to -the d.ifferential
expansion between the ceramic and its case.
For this purpose, the body of ceramic is usually main-
tained inside the case by a metal netting or trellis which
provides its suspension.
Unfortunately, this metal trellis does not resist high
temperatures which may reach ~00 to 1 OOoC to which the
exhaust gases are brought. A sealing element is therefore
necessary for isolating the metal trellis from tne gas in
let chamber. However, it is found that this sealing element
has a tendency to deteriorate,which results in the deterio-
ration of the trellis, so that not only the body of ceramic
material is no longer held in position, a part of the exhaust
~asesmay flow around the body of ceramic material in the
spacetherebetween and the case, so that it is not -treated.
An object of the present invention is to overcome
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this drawback by providing a catalytic exhaust muffler which
affords great safety in operation and in particular in the main-
tenance of the position of the body of ceramic material.
The invention therefore provides a catalytic exhaust
muffler comprising at least one body of ceramic material, of the
honeycomb type, a metal case coaxially enclosing the body and
defining with the body an annular space around the body and inlet
and outlet chambers at axially opposi-te ends of the body a blanket
of fibres interposed between the body and the case in said annular
space, the fibres of the blanket being very resistant to high
temperatures, said blanket being substantially devoid oE hi:nder
and devoid o:E water of cons-t.Ltu-tLon and bc:ing highly compre~sscd
between the body and -th~ case, saicl case compr:isLncJ two ha:l:E shel:ls
and means interconnecting said half-shells, each half-shelL having
axially opposite end portions extending toward the axis of the
body inwardly beyond an outer periphery of the body, and a sealing
element surrounding an end of the body of ceramic material which
is the closest to the outlet chamber and is compressed between said
case and said body.
The constitution of the blanket of Eibres and its com-
pression enable it not only to absorb differential expansions and/
or vibrations but also to form a barrier against the passage of
the gases between the body of ceramic material and the case, which
ensures high efficiency of the exhaust muffler, even at very high
temperatures.
According to a feature of the invention, the blanket
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of fibres surrounds the whole of the body of ceramic material.
The sealing element may be formed by a closely braided
cord of fibres very resistant to high temperatures, similar
to those which constitute the blanket, or by a thermoexpansible
material.
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According tG another embodiment, the blanket is made
in two paris, each of which has a length close to that of
one of the large-diameter portions of the body of ceramic
material~ and are spaced from each other.
The following description of embodiments given by way
of non-limiting examples ana shown in the accompanying draw-
ings will bring out the features and advantages of the
invention. In the drawings :
Fig. 1 is a diagrammatic axial sectional view of an
10 exhaust muffler according to the inven-tion ;
Fig. 2 is a sectional view taken on line 2-2 of Fig~ls
Fig. 3 i~ a vlew siMilar to Fi~. 2 of a varlant.
The ca-talytic exhaust mufEler illustrated in the
drawings comprises in the conventional manner a case 1
15 having a substantially elliptical cross-sectional shape
whose two end portions 2 and 4 have pro~ressively decreas-
ing diameters for the purpose of being secured to exhaust
gas inlet and outlet pipes 6 and 8 respectively. Each of
the pipes 6 and 8 preferably carries a fixing flange 10 for
20 securing exhaust piping.
Mounted inside the case 1 is a body 12 which has an
elliptical cross-sectional shape similar to that of the cen
tral portion 14 of the case 1 but with slightly smaller dia-
meters. This body 12 thus defines with the narrowed portions
25 2 and 4 of the case 1 an inlet chamber 16 and an outlet cham
ber 18 for the exhaust gases. It also puts these chambers
16 and 18 in communication with each other, since it includes
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multiple internal passageways, for example in the form of
a honeycomb structure.
Interposed between the body 12 of ceramic material and
the case 14 is a blanket of fibres which is highly com-
pressed and ensures the suspension of the body 12. Theblanket 20, 22 is formed by so-called long fibres having
for example diameters of 2 to 10 ~ and a high resistance
to high temperatures and to most of the corrosive agents
in an oxidizing or reducing atmosphere. Further, the blan-
ket o fibres contains only a very small ~uan-tity o~ ~inde~,
preEerably le~s than 2 ~ and substantially no water o~
constitution. Particularly suitable blankets are for
example those made from compound fibres based on magnesia
and/or lime and/or alumina and/or silica and in particular
the ceramic fibre sold by the firm Carborandum under the
name "Fibermax Buck Fiber".
The blanket is moreover highly compressed under a
pressure on the order of 2 met,ric tons which reduces i-ts
thickness to 1/4 or 1/5th o~ its initial value.
In the embodiment shown in Fig. 2, the blanket is made
in two juxtaposed parts~each of which covers one half of
the outer surface of the body 12 of ceramic material, and which
are clamped against each other in the case 1.
A sealing element 24 is moreover mounted around the
body 12 in the vicinity of the exhaust gas outlet chamber
18 which it separates from the blanket 20, 22. This seal-
ing element may be made from any suitahle material, but is
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preferably formed by a cord of closely braided fibres
constituted by fibres similar to those constituting the
blanket, i.e. fibres having a very good resistance to high
temperatures and also having a high resistance to corro-
sive agents, or from a band of thermoexpansible materialsuch as thermoex?ansible paper sold by the firm Carborandum
under the name "Fiberfrax XPE-3100 Paper". This band is
simply wound around the body 12, the ends being cut into
tenons and mortises for afEordlng the seal.
According to the variant shown in Flg. 3, the blanket
is made ln -two par-ts 30 ~nd 32 which are spaced apart and
cover only a part of the ceramic body 12, each o the parts
30, 32 of the blanket however extending over a length suf-
ficient to cover at least the major part of the surfacs of
large diameter of the body 12. In the embodiment shown
in Fig. 3, each part of the blanket in fact extends over
the whole of the surface of large diameter of the body 12
and is even extended in a portion of the surface of small
diameter. A space 34, 36 is thus provlded at two opposed
points of the cross-section of the exhaust muffler between
the two blanke-ts 30 and 32.
In this embodiment, as in the preceding embodiment,
the blankets 30 and 32 are highly compressed and this com-
pression combined with the nature of the fibres from which
the blankets are made enable them not only to resist high
temperatures, such as those of exhaust gases entering the
inlet chamber 16, but also to perform the function of a
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sealing element preventing the passage of these hot gases
around the ceramic body 12. It will be understood that
the spaces 34 and 36 allow a stream of gas through bu-t
this stream is sto~ped in a extremely reliable manner by the
sealing element 24 which prevents their entry into the
outlet chamber 18 and obliges them to pass through the
body 12.
The blankets 20 and 22 ensure an almost total seal.
In any case, the gases which reach the sealing element 24
have been considerably cooled and are at a t:emperat~lre
which i~ distinctly lower than that o~ -th~ inlet chamb~r 16.
~isks of det~rioration oE the sealing element are therefore
extremely reduced.
The exhaust muffler therefore has an excellent resis-
tance to temperature and this enables it to be used for along time with high efficiency.
It is moreover extremely simple to assemble. Indeed,
the blankets 20, 22 or 30, 32,whose initial thickness is
on the order of 20 mm,are first of all placed on the outer
surface of the ceramic body 12 by leaving at the end of the
latter place for the sealing element 24. This sealing
element is then placed in position around the body 12 and
then the assembly is inserted in one of the semi-shells 26
adapted to form the case 1. The second semi-shell 28 is
then applied,with a pressure of a few metric tons~on the
blanket remote from the semi-shell 26 and compressed until
it comes into contact with this semi-shell, the blankets
20, 22 or 30, 32 then having a thickness on the order of
4 to 5 mm. At this moment, the semi-shells 26 and 28 are
welded together and the exhaust muffler constitutes a
coherent unit ready to be placed in position.
Although the embodiment just described concerns an
exhaust muffler comprising only a single body 12 of cera-
mic, it will be clear that an exhaust muEfler according to
the invention may have a plurality of similar bodies moun-
ted in the same case in such manner as to be passed through
in succession by the exhaust gases and each maintained in
po~1-tion by a compressecl blanke-t of fibres in one or more
parts, and a sealing element 24 at their end which is the
closest to the gas outlet chamber.
